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DS1302

Trickle Charge Timekeeping Chip

DS1302

041697 1/12

FEATURES

• Real time clock counts seconds, minutes, hours, date

of the month, month, day of the week, and year with

leap year compensation valid up to 2100

• 31 x 8 RAM for scratchpad data storage

• Serial I/O for minimum pin count

• 2.5–5.5 volt full operation

– Optional 2.0–5.5 volt full operation also available

• Uses less than 300 nA at 2.5 volts

• Single–byte or multiple–byte (burst mode) data trans-

fer for read or write of clock or RAM data

• 8–pin DIP or optional 8–pin SOIC’s for surface mount

• Simple 3–wire interface

• TTL–compatible (V

= 5V)

• Optional industrial temperature range –40°C to +85°C

• DS1202 compatible

• Added features over DS1202

– Optional trickle charge capability to V

CC1

– Dual power supply pins for primary and backup

power supplies

– Backup power supply pin can be used for battery

or super cap input

– Additional scratchpad memory (7 bytes)

PIN ASSIGNMENT

DS1302

CC1

SCLK

I/O

RST

CC2

GND

CC1

SCLK

I/O

RST

CC2

GND

DS1302S 8–PIN SOIC (200 MIL)

8–PIN DIP (300 MIL)

DS1302Z 8–PIN SOIC (150 MIL)

PIN DESCRIPTION

X1, X2 – 32.768 kHz Crystal Pins

GND – Ground

RST – Reset

I/O – Data Input/Output

SCLK – Serial Clock

CC1

, V

CC2

– Power Supply Pins

ORDERING INFORMATION

PART # DESCRIPTION

DS1302 Serial Timekeeping Chip; 8–pin DIP

DS1302S Serial Timekeeping Chip;

8–pin SOIC (200 mil)

DS1302Z Serial Timekeeping Chip;

8–pin SOIC (150 mil)

DESCRIPTION

The DS1302 Trickle Charge Timekeeping Chip contains

a real time clock/calendar and 31 bytes of static RAM. It

communicates with a microprocessor via a simple serial

interface. The real time clock/calendar provides

seconds, minutes, hours, day, date, month, and year

information. The end of the month date is automatically

adjusted for months with less than 31 days, including

corrections for leap year. The clock operates in either

the 24–hour or 12–hour format with an AM/PM indicator.

Interfacing the DS1302 with a microprocessor is simpli-

fied by using synchronous serial communication. Only

three wires are required to communicate with the clock/

RAM: (1) RST (Reset), (2) I/O (Data line), and (3) SCLK

(Serial clock). Data can be transferred to and from the

clock/RAM one byte at a time or in a burst of up to 31

bytes. The DS1302 is designed to operate on very low

power and retain data and clock information on less

than 1 microwatt.

Summary of content (12 pages)

PAGE 1
DS1302 DS1302 Trickle Charge Timekeeping Chip FEATURES PIN ASSIGNMENT • Real time clock counts seconds, minutes, hours, date of the month, month, day of the week, and year with leap year compensation valid up to 2100 • 31 x 8 RAM for scratchpad data storage • Serial I/O for minimum pin count VCC2 1 8 VCC1 X1 2 7 SCLK X2 3 6 I/O GND 4 5 RST DS1302 8–PIN DIP (300 MIL) • 2.5–5.5 volt full operation – Optional 2.0–5.
PAGE 2
DS1302 After the first eight clock cycles have loaded the command word into the shift register, additional clocks will output data for a read or input data for a write. The number of clock pulses equals eight plus eight for byte mode or eight plus up to 248 for burst mode. The DS1302 is the successor to the DS1202.
PAGE 3
DS1302 RESET AND CLOCK CONTROL All data transfers are initiated by driving the RST input high. The RST input serves two functions. First, RST turns on the control logic which allows access to the shift register for the address/command sequence. Second, the RST signal provides a method of terminating either single byte or multiple byte data transfer. A clock cycle is a sequence of a falling edge followed by a rising edge.
PAGE 4
DS1302 TCS. The RS bits (bits 0 – 1) select the resistor that is connected between VCC2 and VCC1. The resistor selected by the resistor select (RS) bits is as follows: RS Bits Resistor Typical Value 00 None None 01 R1 2KΩ 10 R2 4KΩ 11 R3 8KΩ If RS is 00, the trickle charger is disabled independent of TCS. Diode and resistor selection is determined by the user according to the maximum current desired for battery or super cap charging.
PAGE 5
DS1302 DATA TRANSFER SUMMARY Figure 3 SINGLE BYTE TRANSFER SCLK RST 0 R/W I/O 1 2 A0 A1 3 A2 4 A3 5 6 7 A4 R/C 1 0 1 2 ADDRESS COMMAND 3 4 5 6 7 DATA INPUT/OUTPUT BURST MODE TRANSFER SCLK RST 0 R/W I/O 1 1 2 1 3 1 4 1 5 6 7 1 R/C 1 ADDRESS COMMAND 0 1 DATA I/O BYTE 1 FUNCTION BYTE N SCLK n CLOCK 8 72 RAM 31 256 2 4 5 6 7 DATA I/O BYTE N 041697 5/12
PAGE 6
DS1302 REGISTER ADDRESS/DEFINITION Figure 4 REGISTER ADDRESS A.
PAGE 7
DS1302 DS1302 PROGRAMMABLE TRICKLE CHARGER Figure 5 R1 2KΩ VCC1 VCC2 R2 4KΩ PIN #8 PIN #1 R3 8KΩ 1 OF 16 SELECT 1 OF 2 SELECT (NOTE: ONLY 1010 CODE ENABLES CHARGER TRICKLE CHARGE REGISTER 1 OF 3 SELECT TCS TCS TCS TCS DS DS RS RS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 TCS = TRICKLE CHARGER SELECT DS = DIODE SELECT RS = RESISTOR SELECT 041697 7/12
PAGE 8
DS1302 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature –0.5V to +7.0V 0°C to 70°C –55°C to +125°C 260°C for 10 seconds * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
PAGE 9
DS1302 DC ELECTRICAL CHARACTERISTICS (cont’d) PARAMETER Timekeeping Current Standby Current SYMBOL ICC2T ICC2S (0°C to 70°C; VCC = 2.5 to 5.5V*) MIN TYP MAX VCC2=2.5V 25.3 VCC2=5V 81 VCC2=2.5V 25 VCC2=5V 80 UNITS NOTES µA 4 13 4,13 µA 10 13 10, Trickle Charge Resistors R1 R2 R3 2 4 8 KΩ KΩ KΩ Trickle Charger Diode Voltage Drop VTD 0.7 V *Unless otherwise noted.
PAGE 10
DS1302 (0°C to 70°C; VCC = +5V ± 10%*) AC ELECTRICAL CHARACTERISTICS (cont’d) PARAMETER SYMBOL CLK to RST Hold tCCH RST Inactive Time tCWH RST to I/O High Z tCDZ SCLK to I/O High Z tCCZ MIN VCC =2.5V 240 VCC=5V 60 VCC=2.5V 4 VCC=5V 1 TYP MAX VCC=2.5V 280 VCC=5V 70 VCC=2.5V 280 VCC=5V 70 UNITS NOTES ns 7 µs 7 ns 7 ns 7 *Unless otherwise noted.
PAGE 11
DS1302 NOTES: 1. All voltages are referenced to ground. 2. Logic one voltages are specified at a source current of 1 mA at VCC=5V and 0.4 mA at VCC=2.5V, VOH=VCC for capacitive loads. 3. Logic zero voltages are specified at a sink current of 4 mA at VCC=5V and 1.5 mA at VCC=2.5V, VOL=GND for capacitive loads. 4. ICC1T and ICC2T are specified with I/O open, RST set to a logic “0”, and clock halt flag=0 (oscillator enabled). 5.
PAGE 12
DS1302 DS1302S SERIAL TIMEKEEPER 8–PIN SOIC (150 MIL AND 200 MIL) 8–PIN (150 MIL) PKG DIM MIN MAX MIN MAX A IN. MM 0.188 4.78 0.196 4.98 0.203 5.16 0.213 5.41 B IN. MM 0.150 3.81 0.158 4.01 0.203 5.16 0.213 5.41 C IN. MM 0.048 1.22 0.062 1.57 0.070 1.78 0.074 1.88 E IN. MM 0.004 0.10 0.010 0.25 0.004 0.10 0.010 0.25 F IN. MM 0.053 1.35 0.069 1.75 0.074 1.88 0.084 2.13 G IN. MM 0.050 BSC 1.27 BSC H IN. MM 0.230 5.84 0.244 6.20 0.302 7.67 0.318 8.08 J IN. MM 0.007 0.